Has anyone fitted an OBX or similar throttle bodies kit? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

edc · 09-27-2013, 03:53 PM

If so I'd like to hear more - costs, unexpected problems, extra bits, gains, mapping etc.

The Radium King · 10-01-2013, 06:39 AM

i'd looked into itb's for a 911 project before, but first i'd heard that they make them for the m96 engines. first concern would be fit in the boxster. geometry aside, in searching around I found some cool info on alpha-n tuning - running the car without a maf (required with itb's) and just using tps. the bosche ecu can do it (that's how it runs in 'limp' mode') so it's just a matter of tweaking it for performance and accuracy (and fining a place for your iat sensor, and rigging a cable throttle that also has a tps sensor that speaks to the ecu). apparently chip wizards in the uk has experience with this. so, with tuning addressed you just need vacuum. there's a variety of electric vacuum pumps on the market, but uncertain if they can handle the crap that comes out of the aos (you want to keep vacuum on the crankcase to seal the rings); if so you can just vent it to a catch-can that you drain occasionally.

The Radium King · 10-01-2013, 07:08 AM

not a lot of info out there on alpha-n tuning for Porsche. seems to be a lot of use on bmw's, due to the fact that the m-sport cars come with itbs so no maf. apparently some Porsche gt3 race teams run alpha-n, not because they have itb's, but because it gets the maf out of the intake for less restriction. seems like it could be a tuning option for any boxster owner - if you're gonna pay $1000 for a softronic tune, why not pay something similar and get the maf out of there altogether (less restriction, no fouling issues, etc.)? of course, you can't modify fuel trim for air density ...

The Radium King · 10-01-2013, 07:36 AM

another way to avoid ditching the current ecu would be to go wideband 02 and piggyback. disconnect the maf and let the car go into limp mode (disconnect the cel to avoid the pesky orange light) then use the piggyback to add fuel based on what the wideband sees. uncertain if limp mode messes with timing, however ...

Bigsmoothlee · 10-02-2013, 04:11 AM

Ditching the maf and tuning with a piggy back isnt as easy as you say it is.

Youll need a very good manifold pressure sensor to start, and then the rest is programming. Now, a few issues to running ITBs and alpha n...

Space for an air filter ( which is MANDATORY for a mid engine )
Length of the runners
Alpha N seems to only be good for idle and WOT, and nothing in between

Between this, some good camshafts and headwork, you should be able to pull close to 100hp/liter if done correctly.

The Radium King · 10-02-2013, 05:47 AM

i thought alpha n didnt need to know manifold pressure? i thought it was purely a tps thing ( the bosch ecu doesnt have a manifold pressure sensor and these guys are getting it done with just the oem ecu). if you are going stand-alone fueling then yeah run a pressure sensor in conjunction with tps. i could see how tuning from just tps could get very on/off (trying to use a 0 to 5v signal to calculate fueling over a 7000 rpm range - this is why the stand-alone units use the pressure signal as well) but ive driven my car in limp mode, which is presumably just running on tps, and it is quite responsive. but i could see a lot of finesse and tuning being required. and no idea how youd fit it in a boxster.

The Radium King · 10-23-2013, 04:30 PM

just found this:

cam tweak, early 996 cup - Rennlist Discussion Forums

the poster works (owns?) blitzkrieg autowerks in Vancouver; you could contact him for more info on itbs.

Kenny Boxster · 10-23-2013, 08:25 PM

It's been done before.

A British rally driver, Mr. Ian Jemison would probably be the person I would want to talk to. He did quite a bit of work to a boxster. I wonder what power he is making! I believe he also swapped to a 3.6 or 3.4 engine too.